import type { List } from ".";
import type { Args, GenericFn, GenericResolver } from "../HKT";
import type { Broaden } from "../helpers";

/**
 * Concatenate two {@link List}s.
 *
 * Sig: `<T>(xs: List<T>, ys: List<T>) => List<T>`
 */
export type Concat<TS extends List, US extends List> =
  TS extends unknown[] ? [...TS, ...US] : readonly [...TS, ...US];

interface Resolver extends GenericResolver<[List, List], List> {
  on1_: ([xs]: Args<this>) => [
    [List<Broaden<(typeof xs)[number]>>],
    List<Broaden<(typeof xs)[number]>>,
  ];
  on_1: ([, ys]: Args<this>) => [
    [List<Broaden<(typeof ys)[number]>>],
    List<Broaden<(typeof ys)[number]>>,
  ];
  on11: ([xs, ys]: Args<this>) => [[], List<(typeof xs)[number] | (typeof ys)[number]>];
}

/**
 * [Fn] Concatenate two {@link List}s.
 *
 * Sig: `<T>(xs: List<T>, ys: List<T>) => List<T>`
 */
export default interface ConcatFn extends GenericFn<Resolver> {
  def: ([xs, ys]: Args<this>) => Concat<typeof xs, typeof ys>;
}